Global routine vaccination coverage 2011

Published in the Weekly Epidemiological Record on 2 November 2012

In 1974, WHO established the Expanded Programme on
Immunization to ensure that all children had access to
routinely recommended vaccines.1 Global coverage with
the third dose of diphtheria–tetanus–pertussis vaccine
(DTP3) was <5% in 1974 and increased to 79% by 2005;
however, more than one-fifth of the world’s children,
especially those in low-income countries, were still not
fully vaccinated. In 2005, WHO and UNICEF developed
the Global Immunization Vision and Strategy (GIVS) to
improve national immunization programmes and decrease
morbidity and mortality associated with vaccinepreventable
diseases.2 One goal of the strategy was that
all countries achieve and sustain 90% national DTP3
coverage.

This report summarizes global routine vaccination coverage
during 2011. An estimated 83% of infants worldwide
received at least 3 doses of DTP vaccine in 2011,
similar to coverage in 2009 (83%) and 2010 (84%).
Among 194 WHO member states, 130 (67%) achieved
≥90% national DTP3 coverage. However, 22.4 million
children were incompletely vaccinated at 12 months of
age and remained at risk for vaccine-preventable morbidity
and mortality. More than half of all incompletely
vaccinated children live in 3 countries: India (32%),
Nigeria (14%), and Indonesia (7%). Among all incompletely
vaccinated children, 62% never received the first
DTP dose (DTP1), and 38% started but never completed
the series. Strengthening routine immunization services,
especially in countries with the greatest number
of under-vaccinated children, should be a global priority
to help achieve the fourth Millennium Development
Goal, to reduce mortality among children <5 years of
age by two-thirds from 1990 to 2015.

Vaccination coverage is calculated as percentage of
those in the target age group who received a dose of a
recommended vaccine by a given age. DTP3 coverage
by age 12 months is a major indicator of immunization
programme performance, but coverage with other vaccines,
such as third dose of oral polio vaccine (OPV3)
or first dose of measles-containing vaccine (MCV1) is
also considered. Administrative coverage estimates are
derived by dividing the number of vaccine doses administered
to children in the target age group by the
estimated target population. These are reported annually
to WHO and UNICEF by 194 WHO member states
through the Joint Reporting Form. Further estimates
of vaccination coverage can be obtained from coverage
surveys in which a representative sample of households
is visited to identify children in the target age group, and dates of receipt of vaccine doses are copied from
the child’s vaccination card. If the card is not available,
a caregiver is asked to recall whether the child received
a particular vaccine dose. WHO and UNICEF derive national
estimates of vaccination coverage through an annual
country-by-country review of all available data,
which may include revision of the historical coverage
time series. These estimates are updated and published
annually on the WHO website.

By the end of 2011, hepatitis B vaccine was introduced
into routine childhood vaccination schedules in
180 (93%) countries; 94 (52%) recommended the first
dose within 24 hours of birth to prevent perinatal transmission
of hepatitis B virus infection. Coverage with
3 doses of Haemophilus influenzae type b vaccine
(Hib3), which had been introduced in 177 (91%) countries
by 2011, was 43% globally, ranging from 11%
(South-East Asia Region) to 90% (Region of the Americas).
By 2011, rotavirus vaccine had been introduced in
31 (16%) countries, and pneumococcal conjugate vaccine
(PCV) in 72 (37%) countries.

Editorial note

Administrative coverage estimates are convenient and
timely, but may overestimate or underestimate coverage
if there are inaccuracies in the numerator (i.e.
doses administered) or denominator (i.e. census data).
While coverage surveys are not dependent on knowledge
of target population size or on other administrative
data sources, they are costly and, because they are
retrospective, are not timely. Further, accuracy and
precision of coverage survey estimates decrease as
proportion of cardholders decreases. Unfortunately,
the prevalence of cardholders is low in many countries.
6 In 87 countries with available card prevalence
data from demographic and health surveys or multiple
indicator cluster surveys since 2000, the median prevalence
of cardholders was 72% (range: 8%–99%), but
prevalence was <70% in 21 of the 33 least-developed
countries (according to World Bank classification)
(median: 62%; range: 8%–93%).

Coverage surveys are useful for validating administrative
data and for monitoring coverage at different administrative
levels, to aid in identifying areas of low
coverage. WHO recommends that countries conduct
regular vaccination coverage surveys to validate
reported administrative coverage. A WHO advisory
committee recommends validation of vaccine coverage
estimates, ideally using multiple external data sources
such as serosurveys, mortality and morbidity data.

Among all incompletely vaccinated children worldwide,
14 million (62%) had not received the first DTP dose.
Nearly 8.4 million received at least one DTP dose, but
dropped out before completing the 3-dose series. The
factors associated with under-vaccination may be different
from those associated with non-vaccination.8 For
example, immunization system issues are more commonly
reported with under-vaccination while access to
services, parental attitudes, knowledge and practices
appear to play a greater role among children who have
not received any vaccination. For improvements in
global vaccination coverage to occur, multifaceted and
tailored strategies will be required by countries to address
the factors contributing to incomplete infant vaccination,
particularly among countries with the largest
number of unvaccinated children.

More than half of incompletely vaccinated children
live in 3 countries (India, Nigeria and Indonesia).
Focusing routine immunization efforts in countries
with the highest number of unvaccinated children
should substantially reduce the number of susceptible
children worldwide and limit the occurrence and
spread of vaccine-preventable disease outbreaks. As
part of the Decade of Vaccines launched in 2010, a
global vaccine action plan was adopted by all WHO
member states at the World Health Assembly in May
2012.9 Meeting routine vaccination coverage targets in
every region, country and community worldwide is a
major goal of this plan.